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. 2021 Dec:60:101533.
doi: 10.1016/j.smrv.2021.101533. Epub 2021 Aug 4.

I think I'm sleepy, therefore I am - Awareness of sleepiness while driving: A systematic review

Anna W T Cai  1 , Jessica E Manousakis  1 , Tiffany Y T Lo  1 , James A Horne  2 , Mark E Howard  3 , Clare Anderson  4
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I think I'm sleepy, therefore I am - Awareness of sleepiness while driving: A systematic review

Anna W T Cai et al. Sleep Med Rev. 2021 Dec.

Abstract

Driver drowsiness contributes to 10-20% of motor vehicle crashes. To reduce crash risk, ideally drivers would be aware of the drowsy state and cease driving. The extent to which drivers can accurately identify sleepiness remains under much debate. We systematically examined whether individuals are aware of sleepiness while driving, and whether this accurately reflects driving impairment, using meta-analyses and narrative review. Within this scope, there is high variability in measures of subjective sleepiness, driving performance and physiologically-derived drowsiness, and statistical analyses. Thirty-four simulated/naturalistic driving studies were reviewed. To summarise, drivers were aware of sleepiness, and this was associated to physiological drowsiness and driving impairment, such that high levels of sleepiness significantly predicted crash events and lane deviations. Subjective sleepiness was more strongly correlated (i) with physiological drowsiness compared to driving outcomes; (ii) under simulated driving conditions compared to naturalistic drives; and (iii) when examined using the Karolinska sleepiness scale (KSS) compared to other measures. Gaps remain in relation to how age, sex, and varying degrees of sleep loss may influence this association. This review provides evidence that drivers are aware of drowsiness while driving, and stopping driving when feeling 'sleepy' may significantly reduce crash risk.

Keywords: Driving performance; Drowsiness; Drowsy driving; Objective sleepiness; Sleepiness; Subjective sleepiness.

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Conflict of interest statement

Conflicts of interest No authors report any conflicts of interest related to the current manuscript. In the interest of full disclosure. JEM reports receiving contract research funding from VicRoads/The Department of Transport, Victoria. MH has received research support from VicRoads, The National Transport Commission, Australian Automobile Association, Seeing Machines Ltd and Optalert Ltd, was a Theme Leader in the Cooperative Research Centre for Alertness, Safety and Productivity and serves an expert witness for Victoria Police and Transport Safety Victoria. CA has received a research award/prize from Sanofi-Aventis; contract research support from VicRoads, Rio Tinto Coal Australia, National Transport Commission, Australian Automobile Association, CogState Ltd, Seeing Machines Ltd, and Tontine/Pacific Brands; and lecturing fees from Brown Medical School/Rhode Island Hospital, Ausmed, Healthmed, TEVA Pharmaceuticals and Philips Healthcare. In addition, she has served as a consultant through her institution to the Rail, Bus and Tram Union, the Transport Accident Commission (TAC), the National Transportation Committee (NTC) and the Department of Transport Victoria. She has also served as an expert witness and/or consultant in relation to fatigue and drowsy driving. CA was a Theme Leader in the Cooperative Research Centre for Alertness, Safety and Productivity.

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